The present invention relates in general to document feeders for reproduction apparatus, and more particularly to a power lift device for automatically raising and lowering a document feeder of a reproduction apparatus.
Reproduction apparatus available today, such as copier/duplicators or printers and the like, have become more complex and versatile in operation. They are extremely sophisticated and can accomplish a wide range of reproduction routines. In typical commercial electrostatographic reproduction apparatus, a latent image charge pattern is formed on a uniformly charged dielectric member. Pigmented marking particles are attracted to the latent image charge pattern to develop such image on the dielectric member. A receiver member (for example, a cut sheet of plain bond paper) is then brought into contact with the dielectric member. An electric field, such as provided by an electrically biased roller or corona charger, is applied so as to effect transfer of the marking particle developed image to the receiver member from the dielectric member. After transfer, the receiver member bearing the transferred image is separated from the dielectric member and transported away from the dielectric member to a fuser assembly at a downstream location. At the fuser assembly, the image is fixed to the receiver member by heat and/or pressure to form a permanent reproduction thereon.
In order to increase the productivity and ease of use of such electrostatographic reproduction apparatus, it has been common practice to provide such apparatus with automatic document handlers. Early document handlers accepted a document sheet set stack and removed individual sheets from the stack one at a time. The removed document sheet was delivered to the exposure platen of the reproduction apparatus, where the desired number of copies of such document sheet were made, and then returned to the stack. Such copy sequence necessitated the use of an auxiliary device, such as a sorter for example, in conjunction with the reproduction apparatus to provide collated reproduction sets.
More recently, automatic document handlers, typically referred to as recirculating document feeders, have been developed which eliminate the need for sorter devices. Recirculating document feeders, such as shown for example in U.S. Pat. No. 4,169,674 (issued Oct. 2, 1979, in the name of Russel) deliver document sheets seriatem from a document sheet set stack to the exposure platen of the reproduction apparatus and return the sheets to the document stack in order. Typically, at the exposure platen only one copy of each document sheet is made for each circulation of the document sheets set stack. The desired number of copies is obtained by recirculating the document sheet set stack a number of times corresponding to the desired number of copies. By such copy sequence, the copy sheet output corresponding to the document sheet set stack is received at the output of the reproduction apparatus in collated order.
While document feeders, of either type, have proven very popular in that they enhance productivity and increase the ease of use of the reproduction apparatus, they require complex construction to reliably handle the document sheets in a manner which will prevent damage to the sheets during transport. Further, the document feeders are cumbersome, and require intricate counterbalance mechanisms to enable them to be manually raised (and lowered) for operator access to the exposure platen of the associated reproduction apparatus. In certain instances, because the document feeders require manual raising and lowering, physically challenged individuals are not able to gain access to the reproduction apparatus exposure platen because of their physical limitations and the construction of the document feeders. Particularly, such individuals may not be able to raise and/or lower the document feeder due to lack of strength or inability to reach to the full extent necessary for raising and lowering the feeder (such as when confined to a wheel chair).